[JENA-1294] JenaSystem.init from RDFS throws NPE, fails ARQ tests

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: Jena 3.2.0
• Fix Version/s: Jena 3.3.0
• Component/s: ARQ, Core

Environment

OpenJDK 1.8.0_121-b13
Linux 4.9.8-1-ARCH #1 SMP PREEMPT x86_64 GNU/Linux

• Assignee: Andy Seaborne
• Reporter: Alexis Armin Huf
• Created: 21/Feb/17 02:27
• Updated: 10/May/17 15:35
• Resolved: 28/Feb/17 23:06

Description

As discussed in #JENA-1290, jena-arq tests failed but committers could not reproduce the issue. The cause was that for some reason the first test that ran on was TestParameterizedSparqlString.test_param_string_injection_01, and as the following stack trace shows, it reached JenaSystem.init from RDFS class initialization.

At least 3 locations involved in core and ARQ initalization refer to RDFS.subClassOf and RDFS.member which are null and cannot be initialized because RDFS is already being initialized:

Init: JenaInitLevel0
Init: InitJenaCore
JenaCore.init - start
RDF: http://www.w3.org/1999/02/22-rdf-syntax-ns#
RDFS: http://www.w3.org/2000/01/rdf-schema#
RDFS.subClassOf: null
OWL: http://www.w3.org/2002/07/owl#
JenaCore.init - finish
Init: InitRIOT
RIOT.init - start
RIOT.init - finish
Init: InitARQ
ARQ.init - start
ARQ.init - start.1
ARQ.init - start.2
ARQ.init - start.3
ARQ.init - start.4
AssemblerUtils.init - start
AssemblerUtils.init.registerDataset - start
implementWith(http://jena.hpl.hp.com/2005/11/Assembler#DefaultModel)
RDFS.subClassOf==null: true
nulls: 5876a9af 7993aa96 null e1204e1f
java.lang.NullPointerException
	at org.apache.jena.rdf.model.impl.ModelCom.add(ModelCom.java:1192)
	at org.apache.jena.assembler.assemblers.AssemblerGroup$ExpandingAssemblerGroup.implementWith(AssemblerGroup.java:95)
	at org.apache.jena.assembler.ConstAssembler.general(ConstAssembler.java:137)
	at org.apache.jena.sparql.core.assembler.AssemblerUtils.registerDataset(AssemblerUtils.java:72)
	at org.apache.jena.sparql.core.assembler.AssemblerUtils.init(AssemblerUtils.java:61)
	at org.apache.jena.query.ARQ.init(ARQ.java:596)
	at org.apache.jena.sparql.system.InitARQ.start(InitARQ.java:29)
	at org.apache.jena.system.JenaSystem.lambda$init$2(JenaSystem.java:119)
	at java.util.ArrayList.forEach(ArrayList.java:1249)
	at org.apache.jena.system.JenaSystem.forEach(JenaSystem.java:194)
	at org.apache.jena.system.JenaSystem.forEach(JenaSystem.java:171)
	at org.apache.jena.system.JenaSystem.init(JenaSystem.java:117)
	at org.apache.jena.graph.NodeFactory.<clinit>(NodeFactory.java:32)
	at org.apache.jena.rdf.model.impl.ResourceImpl.fresh(ResourceImpl.java:135)
	at org.apache.jena.rdf.model.impl.ResourceImpl.<init>(ResourceImpl.java:85)
	at org.apache.jena.rdf.model.ResourceFactory$Impl.createResource(ResourceFactory.java:297)
	at org.apache.jena.rdf.model.ResourceFactory.createResource(ResourceFactory.java:92)
	at org.apache.jena.vocabulary.RDFS.resource(RDFS.java:36)
	at org.apache.jena.vocabulary.RDFS.<clinit>(RDFS.java:44)
	at org.apache.jena.shared.PrefixMapping.<clinit>(PrefixMapping.java:219)
	at org.apache.jena.query.TestParameterizedSparqlString.test_param_string_injection_01(TestParameterizedSparqlString.java:1382)

The same problem can be observed on a one-liner mwe (jena-rdfs-init):

public class App {
    public static void main(String[] args) {
        System.out.printf("subClassOf URI: %s\n", RDFS.subClassOf.toString());
    }
}

The ARQ test issue can be fixed adding a call to JenaSystem.init (call-init.patch). However, if test order changes for someone, the problem re-appears.

For Both the MWE and the test, replacing RDFS fields used in init code with RDF.getURI()+"localName" fixes it (no-rdfs-on-init.patch). It is a hack and the problem remains for if the MWE uses vocab classes (RDF and OWL) in place of RDFS.

Issue Links

• links to: GitHub Pull Request #218